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Optimization: osiris_log: add reader config option for read-ahead limit #198

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Merged
michaelklishin merged 1 commit into from
Nov 3, 2025
+29 −25
Merged

Optimization: osiris_log: add reader config option for read-ahead limit #198

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3 changes: 2 additions & 1 deletion src/osiris.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -83,7 +83,8 @@
-type reader_options() :: #{transport => tcp | ssl,
chunk_selector => all | user_data,
filter_spec => osiris_bloom:filter_spec(),
read_ahead => boolean()
read_ahead => boolean(),
read_ahead_limit => pos_integer()
}.

-export_type([name/0,
Expand Down
51 changes: 27 additions & 24 deletions src/osiris_log.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -107,7 +107,7 @@
_/binary>>).

-define(SKIP_SEARCH_JUMP, 2048).
-define(READ_AHEAD_LIMIT, 4096).
-define(DEFAULT_READ_AHEAD_LIMIT, 4096).

%% Specification of the Log format.
%%
Expand Down Expand Up @@ -425,7 +425,8 @@
-record(ra,
{on = true :: boolean(),
size = ?HEADER_SIZE_B + ?DEFAULT_FILTER_SIZE :: non_neg_integer(),
buf :: undefined | {Pos :: non_neg_integer(), binary()}
buf :: undefined | {Pos :: non_neg_integer(), binary()},
limit = ?DEFAULT_READ_AHEAD_LIMIT :: pos_integer()
}).
-record(read,
{type :: data | offset,
Expand Down Expand Up @@ -1059,7 +1060,6 @@ init_data_reader_at(ChunkId, FilePos, File,
readers_counter_fun := CountersFun} = Config) ->
case file:open(File, [raw, binary, read]) of
{ok, Fd} ->
RaOn = ra_on(Config),
Cnt = make_counter(Config),
counters:put(Cnt, ?C_OFFSET, ChunkId - 1),
CountersFun(1),
Expand All @@ -1078,7 +1078,7 @@ init_data_reader_at(ChunkId, FilePos, File,
chunk_selector = all,
position = FilePos,
transport = maps:get(transport, Config, tcp),
read_ahead = #ra{on = RaOn}},
read_ahead = ra(Config)},
fd = Fd}};
Err ->
Err
Expand Down Expand Up @@ -1288,7 +1288,6 @@ open_offset_reader_at(SegmentFile, NextChunkId, FilePos,
_ ->
undefined
end,
RaOn = ra_on(Conf),
{ok, #?MODULE{cfg = #cfg{directory = Dir,
counter = Cnt,
counter_id = counter_id(Conf),
Expand All @@ -1303,7 +1302,7 @@ open_offset_reader_at(SegmentFile, NextChunkId, FilePos,
next_offset = NextChunkId,
transport = maps:get(transport, Options, tcp),
filter = FilterMatcher,
read_ahead = #ra{on = RaOn}},
read_ahead = ra(Conf)},
fd = Fd}}.

%% Searches the index files backwards for the ID of the last user chunk.
Expand Down Expand Up @@ -3312,7 +3311,8 @@ iter_guess_size(Credit0, NumEntries, DataSize) ->
Credit = min(Credit0, NumEntries),
(DataSize div NumEntries * Credit).

iter_read_ahead(Fd, Pos, MinReqSize, Credit0, DataSize, NumEntries, Ra0)
iter_read_ahead(Fd, Pos, MinReqSize, Credit0, DataSize, NumEntries,
#ra{limit = ReadAheadLimit} = Ra0)
when is_integer(Credit0) andalso
MinReqSize =< DataSize ->
%% if the minimum request size can be served from read ahead then we
Expand All @@ -3335,7 +3335,7 @@ iter_read_ahead(Fd, Pos, MinReqSize, Credit0, DataSize, NumEntries, Ra0)
%% needed to serve that, else we read up to the readahead
%% limit but not beyond the end of the chunk and not less
%% that the minimum request size
MinSize = max(MinReqSize, min(?READ_AHEAD_LIMIT, DataSize)),
MinSize = max(MinReqSize, min(ReadAheadLimit, DataSize)),
Size = max(MinSize, iter_guess_size(Credit0, NumEntries,
DataSize)),
{ok, Data} = file:pread(Fd, Pos, Size),
Expand Down Expand Up @@ -3364,15 +3364,15 @@ ra_read(_Pos, _Len, _Ra) ->
undefined.

ra_update_size(undefined, FilterSize, LastDataSize,
#ra{on = true, size = Sz} = Ra)
when Sz < ?READ_AHEAD_LIMIT andalso
LastDataSize =< (?READ_AHEAD_LIMIT - ?HEADER_SIZE_B -
#ra{on = true, size = Sz, limit = Limit} = Ra)
when Sz < Limit andalso
LastDataSize =< (Limit - ?HEADER_SIZE_B -
FilterSize - ?REC_HDR_SZ_SUBBATCH_B) ->
%% no filter and last data size was small so enable data read ahead
Ra#ra{size = ?READ_AHEAD_LIMIT};
Ra#ra{size = Limit};
ra_update_size(undefined, FilterSize, LastDataSize,
#ra{on = true, size = ?READ_AHEAD_LIMIT} = Ra)
when LastDataSize =< (?READ_AHEAD_LIMIT - ?HEADER_SIZE_B -
#ra{on = true, size = Limit, limit = Limit} = Ra)
when LastDataSize =< (Limit - ?HEADER_SIZE_B -
FilterSize - ?REC_HDR_SZ_SUBBATCH_B) ->
Ra;
ra_update_size(_Filter, FilterSize, _LastDataSize, #ra{size = Sz} = Ra) ->
Expand All @@ -3397,10 +3397,13 @@ ra_fill(Fd, Pos, #ra{size = Sz} = Ra) ->
Err
end.

ra_on(#{options := #{read_ahead := false}}) ->
false;
ra_on(_) ->
true.
-spec ra(config()) -> #ra{}.
ra(#{options := #{read_ahead := false}}) ->
#ra{on = false};
ra(#{options := #{read_ahead_limit := Limit}}) when is_integer(Limit) ->
#ra{limit = Limit};
ra(_) ->
#ra{on = true}.

generate_log(Msg, MsgsPerChunk, NumMessages, Directory) ->
Name = filename:basename(Directory),
Expand Down Expand Up @@ -3441,28 +3444,28 @@ ra_update_size_test() ->
DefSize = ?HEADER_SIZE_B + ?DEFAULT_FILTER_SIZE,
?assertMatch(#ra{size = DefSize}, #ra{}),
Ra0 = #ra{},
?assertMatch(#ra{size = ?READ_AHEAD_LIMIT},
?assertMatch(#ra{size = ?DEFAULT_READ_AHEAD_LIMIT},
ra_update_size(undefined, ?DEFAULT_FILTER_SIZE, 100, Ra0)),

?assertMatch(#ra{size = ?READ_AHEAD_LIMIT},
?assertMatch(#ra{size = ?DEFAULT_READ_AHEAD_LIMIT},
ra_update_size(undefined, ?DEFAULT_FILTER_SIZE, 100, Ra0)),
Ra1 = #ra{size = ?READ_AHEAD_LIMIT},
Ra1 = #ra{size = ?DEFAULT_READ_AHEAD_LIMIT},
?assertMatch(#ra{size = DefSize},
ra_update_size(undefined, ?DEFAULT_FILTER_SIZE, 5000, Ra1)),

?assertMatch(#ra{size = ?READ_AHEAD_LIMIT},
?assertMatch(#ra{size = ?DEFAULT_READ_AHEAD_LIMIT},
ra_update_size(undefined, ?DEFAULT_FILTER_SIZE, 100, Ra1)),

?assertMatch(#ra{size = DefSize},
ra_update_size("a filter", ?DEFAULT_FILTER_SIZE, 100, Ra0)),

%% we need to ensure that if we enable read ahead we can at least fulfil
%% the prior chunk including header filter and record length header
MaxEnablingDataSize = ?READ_AHEAD_LIMIT - ?HEADER_SIZE_B - ?DEFAULT_FILTER_SIZE - ?REC_HDR_SZ_SUBBATCH_B,
MaxEnablingDataSize = ?DEFAULT_READ_AHEAD_LIMIT - ?HEADER_SIZE_B - ?DEFAULT_FILTER_SIZE - ?REC_HDR_SZ_SUBBATCH_B,
?assertMatch(#ra{size = DefSize},
ra_update_size(undefined, ?DEFAULT_FILTER_SIZE, MaxEnablingDataSize + 1 ,
Ra0)),
?assertMatch(#ra{size = ?READ_AHEAD_LIMIT},
?assertMatch(#ra{size = ?DEFAULT_READ_AHEAD_LIMIT},
ra_update_size(undefined, ?DEFAULT_FILTER_SIZE, MaxEnablingDataSize,
Ra0)),
ok.
Expand Down